Monitoring

Hello,

this is a monitoring module to plot basic quantities which would allow the user to quickly verify fbu was configured correctly.
The monitoring is turned off by default but it can be enabled with
pyfbu.Monitoring = True

(btw...did we ever decide whether we use capital or lower case for fbu options?)

At the moment i'm only plotting the posteriors for each bin compared with the size of the hyperbox and the value in data.
I'd propose  to keep this branch open and keep adding information in the ValidationPlots.py module. We can merge it as soon as we are satisfied.
Please make suggestions about what we should add.
My to do list is:
- plot response matrix
- overlay data and background distributions